Files in this Data Supplement:

• Movie 1 -

  Movie 1. Induced phonation of an avian syrinx. To induce phonation and identify potential sites of sound generation, we used sutures and surgical glue to seal a length of small diameter surgical tubing to the anterior end of the excised vocal tract (trachea, syrinx and anterior-most rings of the bronchi), and attached the other end of the tubing to a standard laboratory air suction pump. We then adjusted the rate of air flow to a level high enough to induce vibrations but low enough to avoid causing the trachea to collapse. To adjust tension, we used manipulated the bronchi using forceps. This technique produces a sound unlike the actual vocalizations of the animal in question, but does allow for identification of potential sites of sound production in a living bird.

• Audio File - MP3 format
• Audio File - WAV format -

  Audio File 1. Audio recording of a sage-grouse display. Here is a single-channel audio recording of the strut display of a male greater sage-grouse (Centrocercus urophasianus), recorded at Monument Lek near Lander, Wyoming, USA. A spectrogram of a display is provided in the text (Fig. 2A). The display begins with mechanically generated ‘swish’ sounds produced by movement of the wings against stiffened breast feathers. These are followed by vocal sounds, starting with low-frequency ‘coo’ notes, a sharp broadband ‘pop’ note, a higher-pitched frequency-modulated ‘whistle’, and ending with a second pop.